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Optical Pickup Apparatus - Patent 8154978

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This application claims the benefit of priority to Japanese Patent Application No. 2007-052769, filed Mar. 2, 2007, of which full contents are incorporated herein by reference.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus executing a reading-out operation of a signal recorded in an optical disc or a recording operation of a signal in the optical disc. 2. Description of the Related Art An optical disc device capable of a reading-out operation and a recording operation of a signal by applying laser light emitted from an optical pickup apparatus to a signal recording layer of the optical disc has been in widespread use. Whilethe optical disc devices using optical discs called CD or DVD are widely available, optical discs in which recording density is improved, that is, those using Blu-ray standard or HD DVD (High Definition Digital Versatile Disc) standard optical discs haverecently been developed. Infrared light with a wavelength of 780 nm is used as the laser light for executing the reading-out operation of a signal recorded in the optical disc of the CD standard, and red light with a wavelength of 650 nm is used as the laser light withwhich the reading-out operation of a signal recorded of the DVD standard optical disc is executed. The thickness of a protective layer provided on a top face of the signal recording layer in the CD standard optical disc is 1.2 mm, and the numerical aperture of an objective lens used for the reading-out operation of a signal from this signalrecording layer, is specified to be 0.45. The thickness of the protective layer provided on the top face of the signal recording layer in the DVD standard optical disc is 0.6 mm and the numerical aperture of the objective lens used for the reading-outoperation of a signal from this signal recording layer is specified to be 0.6. In contrast to the case of such CD-standard and DVD-standard optical discs, in the Blu-ray standard

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